548 



FRESH-WATER BIOLOGY 



17 (18) Embryos from 

 a e 



5 to 108 M long. 



Echinorhynchus thecatus Linton 1892. 



Body cylindrical , slightly curved; proboscis curved also. 

 Female 11 to 26 mm. long; width 0.51 to 0.89, anteriorly 0.8 

 to 1,4 mm. in maximum, 0.52 to i mm. posteriorly. Male 7 

 to 12 mm. long; width 0.39 to 0.69 anteriorly, 0.59 to 0.95 in 

 maximum, 0.37 to 0.75 posteriorly. Hooks in 24 to 31 trans- 

 verse and 1 2 longitudinal rows surrounded by prominent collars. 

 Embr>'os 85 to 108 fx long by 18 to 22 fx broad. (Graybill.) 



In ahmentary canal and body cavity of Micropterus dolo- 

 mieu, Ambloplites rupestris, Amia calva, and Roccus lineatus. 

 Great Lakes and eastern waters. 



Fig. 850. Echinorhynchus thecatus. a, hooks from ventral side of 

 proboscis near base; b. hook from ventral, i.e., concave side of probos- 

 cis; c, hooks from dorsal, i.e., convex side of proboscis. X 150- (After 

 Linton.) 



18 iiyj Embryos from 115 to 165 ix long. . Echinorhynchus salvelini Linkins. 



Male 7 to 9 mm. long, 0.82 to 1.27 mm. broad. Fe- 

 male loto 17 mm. long, 1.2 to 1.6 mm. wide. Proboscis 

 armed with 26 circular rows of 8 hooks each. Hooks 

 alternate in adjacent rows. Basal hooks 39 to 50 /x 

 long; hooks in middle and anterior regions 44 to 68 /i' 

 long, those with basal processes 83 fj. long. Embryos 

 115 to 165 ^l long by 20 to 25 fx wide. 



From lake trout; Lake Michigan. 



Fig. 851. Echinorhynchus salvelini. Optical section through 

 anterior region of bodJ^ X 60. (After Linkins.) 



19 (14) Spines on body at some point at least, usually at anterior end. . 20 



20 (23) Body tapers regularly towards both ends. Proboscis in line with 



axis of body. Posterior limit of spines alike on dorsal and 

 ventral surfaces 21 



21(22) Cement glands tubular Poly morphus Liihe igii. 



Fine spines on skin of anterior body. Just behind the limit of these spines a conspicuous 

 annular constriction. Type species P. minutiis (Goeze) from various European water birds. 

 At least one species yet undescribed from North American Anseriformes. 



22 (21) Cement glands irregularly ovoid. (Males and some females or 

 young specimens.) Filicollis Liihe 191 1. 



Compare number 37 in this key. 



The males, the young females and even some adult females of certain species have a proboscis 

 that departs only slightly from the usual type, being a little enlarged but not conspicuously 



